The VA bilateral factor is a 10 percent addition applied under 38 Code of Federal Regulations (CFR) 4.26 when service-connected disabilities affect both arms, both legs, or paired skeletal muscles. At Rank and Pay, we show how each figure is calculated.
When qualifying paired disabilities exist, the Department of Veterans Affairs (VA) does not calculate the total rating using a single continuous sequence. The VA groups the disabilities affecting the paired limbs or muscle groups first and combines their values. That subtotal receives a 10 percent addition before combining with other service-connected ratings.
What Is the VA Bilateral Factor?
Under 38 CFR 4.26, the bilateral factor provides a 10 percent increase to the combined rating of qualifying paired disabilities before that subtotal is combined with any other service-connected conditions. The regulation governs how the VA rates partial disabilities resulting from disease or injury of both arms, both legs, or paired skeletal muscles.
In standard VA rating calculations under 38 CFR 4.25, ratings are combined sequentially. In that standard process, each new percentage applies only to the remaining non-disabled portion. Consider an initial 20 percent disability.
That 20 percent rating leaves 80 percent non-disabled efficiency. A subsequent 10 percent disability applies only to that remaining 80 percent, adding 8 percent to reach a combined 28 percent. Standard combining continues in that fashion across all conditions.
The bilateral factor alters this basic progression by introducing an intermediate step. When disabilities affect paired extremities or paired muscles, the ratings for the disabilities of the right and left sides are combined first using the 38 CFR 4.25 combined ratings method. Once that paired subtotal is determined, 10 percent of that combined value is added directly to the figure.
The mathematical distinction centers on how that 10 percent is incorporated. Under 38 CFR 4.26, the 10 percent is added to the subtotal instead of combined.
The resulting figure is treated as one disability for later combining. The standard combining method under 38 CFR 4.25 then resumes for all remaining conditions.
Disabilities Covered by the Rule
The bilateral factor applies specifically to service-connected disabilities affecting both arms, both legs, and paired skeletal muscles.
For the lower extremities, the rule covers conditions affecting both legs, such as service-connected ratings affecting both knees. Paired conditions affecting both arms or paired skeletal muscles also fall under 38 CFR 4.26.
More details on paired knee conditions appear on the bilateral knee page. Bilateral hearing loss has its own rating method, as detailed on the bilateral hearing loss page. For Total Disability Based on Individual Unemployability (TDIU), see the guide to TDIU.
Veterans can review the full schedule of disability evaluations across different percentages on the VA disability percentages page.
A Worked Example
A worked mathematical example illustrates how the 10 percent bilateral addition changes a veteran's rating before standard rounding occurs. This calculation serves as an illustration of the formula and does not predict any individual rating. The sequence follows distinct mathematical steps:
- Consider a veteran with a left leg condition rated at 20 percent and a right leg condition rated at 10 percent.
- Combine the two paired leg disabilities first under 38 CFR 4.25: 20 + 10 x (100 - 20) / 100 = 28 percent.
- Calculate 10 percent of that combined bilateral value: 10 percent of 28 is 2.8.
- Add 2.8 directly to 28, which yields 30.8 percent, and 30.8 is treated as 31 percent.
- Combine that 31 percent bilateral value with any remaining disabilities. If this veteran also has one unrelated 10 percent disability, combining 31 and 10 gives 31 + 10 x (100 - 31) / 100 = 37.9 percent, which is about 38 percent.
- The VA rounds the final combined value to the nearest degree divisible by 10 under 38 CFR 4.25, bringing 38 percent to a final rating of 40 percent.
Paired limb ratings are combined together first and augmented with the 10 percent addition. The resulting value is then treated as a single disability when combined with any other service-connected conditions.
Bilateral Factor Versus Standard Combined Ratings
Calculating paired disabilities without the bilateral factor yields a lower unrounded percentage because standard combining applies every rating solely to the remaining non-disabled efficiency. When the VA evaluates multiple disabilities that do not involve paired limbs, every percentage enters the standard sequential combining calculation without an intermediate percentage boost.
To observe the difference, consider the exact same three ratings from the worked example (20 percent, 10 percent, and 10 percent) evaluated without applying 38 CFR 4.26. Standard combined rating procedures are explained on the VA disability rating explained page. The process proceeds through sequential calculation:
- Begin with the largest rating of 20 percent, which leaves the non-disabled portion at 80 percent.
- Apply the first 10 percent rating to the remaining 80 percent: 10 percent of 80 is 8 percent. Adding 8 percent to 20 percent results in 28 percent combined disability, leaving 72 percent non-disabled efficiency.
- Apply the second 10 percent rating to the remaining 72 percent: 10 percent of 72 is 7.2 percent. Adding 7.2 percent to 28 percent yields an unrounded combined rating of 35.2 percent.
Comparing the two intermediate outcomes demonstrates how the bilateral calculation alters the underlying value:
| Calculation Method | Initial Paired Value | Addition (10 Percent) | Intermediate Value | Unrounded Total with Third Rating | Final Rounded Rating |
|---|---|---|---|---|---|
| Standard Combining (No Bilateral Factor) | 28% | None | 28% | 35.2% | 40% |
| Bilateral Factor (38 CFR 4.26) | 28% | +2.8% | 31% (from 30.8%) | 37.9% (about 38%) | 40% |
In this illustration, both calculations round to 40 percent. The VA rounds the final combined value to the nearest degree divisible by 10 under 38 CFR 4.25, and both 35.2 percent and 37.9 percent round to 40 percent. However, the unrounded value produced by the bilateral factor is 2.7 percentage points higher (37.9 percent compared to 35.2 percent).
Checking Your Rating Decision for the Bilateral Factor
A veteran can check their rating decision to see whether the VA applied the bilateral factor to their qualifying conditions. When the VA issues a rating decision involving service-connected disabilities on both arms, both legs, or paired skeletal muscles, the calculation portion of the decision may show it.
The veteran does not file a separate claim for the bilateral factor. The VA applies the factor when it rates the claim based on the service-connected conditions in the file. A veteran might hold service-connected ratings on both legs or both arms without seeing the bilateral factor in the calculation portion. In that situation, an accredited representative can help review the case.
Veterans can test how different combinations of service-connected ratings interact by using the VA disability rating calculator. The calculator estimates combined ratings, and only the VA issues the actual rating. Rank and Pay provides this guide for informational purposes only; it does not constitute legal or benefits advice, and Rank and Pay is not affiliated with the VA.